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Merge pull request #4639 from ethereum/docs-fix-specify-limit

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Small clarifications around the 2300 gas stipend from transfer and send
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Alex Beregszaszi 2018-08-01 16:23:06 +01:00 committed by GitHub
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3 changed files with 6 additions and 3 deletions
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2
docs/common-patterns.rst
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@ -93,7 +93,7 @@ Notice that, in this example, an attacker could trap the
contract into an unusable state by causing ``richest`` to be
the address of a contract that has a fallback function
which fails (e.g. by using ``revert()`` or by just
consuming more than the 2300 gas stipend). That way,
consuming more than the 2300 gas stipend transferred to them). That way,
whenever ``transfer`` is called to deliver funds to the
"poisoned" contract, it will fail and thus also ``becomeRichest``
will fail, with the contract being stuck forever.

5
docs/contracts.rst
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@ -563,7 +563,10 @@ Ether (without data). Additionally, in order to receive Ether, the fallback func
must be marked ``payable``. If no such function exists, the contract cannot receive
Ether through regular transactions.
In the worst case, the fallback function can only rely on 2300 gas being available (for example when send or transfer is used), leaving not much room to perform other operations except basic logging. The following operations will consume more gas than the 2300 gas stipend:
In the worst case, the fallback function can only rely on 2300 gas being
available (for example when `send` or `transfer` is used), leaving little
room to perform other operations except basic logging. The following operations
will consume more gas than the 2300 gas stipend:
- Writing to storage
- Creating a contract

2
docs/security-considerations.rst
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@ -135,7 +135,7 @@ Sending and Receiving Ether
- If a contract receives Ether (without a function being called), the fallback function is executed.
If it does not have a fallback function, the Ether will be rejected (by throwing an exception).
During the execution of the fallback function, the contract can only rely
on the "gas stipend" (2300 gas) being available to it at that time. This stipend is not enough to access storage in any way.
on the "gas stipend" it is passed (2300 gas) being available to it at that time. This stipend is not enough to access storage in any way.
To be sure that your contract can receive Ether in that way, check the gas requirements of the fallback function
(for example in the "details" section in Remix).